Abstracts

Rationale: Despite extensive reports of seizure outcome in temporal lobectomy, quantitative studies examining the relationship between seizure control and the extent of resection are quite limited. Wyler, et al (Neurosurgery:Vol 37(5)November 1995p 982-9911995) reported a higher frequency of seizures if the hippocampus was removed en bloc to the anterior margin of the cerebral peduncle (partial hippocampectomy) than if it was resected to the level of the colliculi (total hippocampectomy). The extent of neocortical resection was 4.5 cm in all patients. Seizure outcomes were not reported in terms of disabling or non-disabling seizures. We now present an analysis of seizure outcomes in a group of patients in which the extent of hippocampal resection was held constant at 4.0 cm but the extent of neocortical resection varied. Methods: Twenty-two consecutive patients with uncomplicated mesial temporal lobe epilepsy (11 left/11 right) underwent a 4.0 cm hippocampectomy (approximately to the base of the colliculi). The fusiform and parahippocampal gyri were resected en bloc. The mean length of neocortical resection was 3.5 cm left (range 3.0-4.0) and 4.7 cm right (range 4.0-5.0).Results: There was no significant left/right difference in pre-surgical seizure frequency. Seizure freedom was present at 12 months after surgery in 54% L and 91% R, and at 24 months 72% L and 81% R. An ANOVA showed a difference for seizure frequency at 12 months post-surgery with right better than left [F=4.759, p=.041]. RTL (mean=.1818, SD=.603) LTL (mean=2.10, SD=2.86). Although L/R seizure frequency was not significantly different at 24 months, seizure disability was significantly less for right temporal lobectomy patients (Chi-square analysis of the major categories I-V of the Engel Classification; [Pearson=8.54, p=.036], [RTL I=10, II=0, III=1, IV=0], [LTL I=4, II=3, III=3, IV=2]. The side of surgery also predicted the Engel classification (using Linear Regression) [F=7.688, p=.011]. Conclusions: Although these findings could be interpreted as a tendency for right temporal lobe epilepsy to be more responsive to surgery, Wyler et al (1995)did not find a L/R difference in outcomes using a similar size group of patients with a constant neocortical and hippocampal (approximately 4.0 cm) resection length. This suggests that the extent of neocortical resection may affect outcome in patients with mesial temporal lobe epilepsy.